U.S. patent number 5,401,307 [Application Number 08/082,602] was granted by the patent office on 1995-03-28 for high temperature-resistant corrosion protection coating on a component, in particular a gas turbine component.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Norbert Czech, Friedhelm Schmitz.
United States Patent |
5,401,307 |
Czech , et al. |
March 28, 1995 |
**Please see images for:
( Certificate of Correction ) ** |
High temperature-resistant corrosion protection coating on a
component, in particular a gas turbine component
Abstract
A protective coating resistant to corrosion at medium and high
temperatures is applied on a nickel-based or cobalt-based
superalloy component. The protective coating essentially consists
of the following elements (in percent by weight): 25 to 40% nickel,
28 to 32% chromium, 7 to 9% aluminum, 1 to 2% silicon, 0.3 to 1% of
at least one reactive element of the rare earths, at least 5%
cobalt; and impurities, as well as selectively from 0 to 15% of at
least one of the elements of the group consisting of rhenium,
platinum, palladium, zirconium, manganese, tungsten, titanium,
molybdenum, niobium, iron, hafnium, and tantalum. The total share
of the elements of the group is from 0 to a maximum of 15% and a
remainder of at least 5% cobalt. The component and the coating
applied thereon have a ductile brittle transition temperature below
500.degree. C.
Inventors: |
Czech; Norbert (Dorsten,
DE), Schmitz; Friedhelm (Dinslaken, DE) |
Assignee: |
Siemens Aktiengesellschaft
(Munich, DE)
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Family
ID: |
24261683 |
Appl.
No.: |
08/082,602 |
Filed: |
June 25, 1993 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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566144 |
Aug 10, 1990 |
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Current U.S.
Class: |
106/14.05;
106/1.21; 106/1.27; 106/1.28; 420/435; 420/441; 428/457 |
Current CPC
Class: |
C23C
4/08 (20130101); C23C 14/16 (20130101); C23C
30/00 (20130101); Y10T 428/31678 (20150401) |
Current International
Class: |
C23C
14/16 (20060101); C23C 4/08 (20060101); C23C
30/00 (20060101); C09D 005/08 (); B32B 015/04 ();
C22C 019/07 () |
Field of
Search: |
;420/435,441
;106/1.21,14.05,1.27,1.28 ;428/457 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0025263 |
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Mar 1981 |
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EP |
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0194392 |
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Sep 1986 |
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EP |
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2463192 |
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Feb 1981 |
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FR |
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2511042 |
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Feb 1983 |
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FR |
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729862 |
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Dec 1942 |
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DE |
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1758010 |
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Dec 1970 |
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DE |
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2355674 |
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May 1974 |
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DE |
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2526683 |
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Jan 1976 |
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DE |
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2095700 |
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Oct 1982 |
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GB |
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2103656 |
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Feb 1983 |
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GB |
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Other References
"The Durability and Performance of Coatings in Gas Turbine and
Diesel Engines", Materials Science & Engineering, 88, 1987, pp.
321-323 no month. .
"Some Effects of Structure and Composition on the Properties of . .
. " Boone, J. Vac. Sci. Technol, vol. 11, No. 4, Jul./Aug. 1974,
pp. 641-646..
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Primary Examiner: Green; Anthony
Attorney, Agent or Firm: Lerner; Herbert L. Greenberg;
Laurence A.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of application Ser. No.
07/566,144, filed Aug. 10, 1990, now abandoned.
Claims
We claim:
1. A protective coating resistant to corrosion applied on a
component formed of a nickel-based or cobalt-based superalloy, the
protective coating consisting essentially of the following elements
(in percent by weight):
25 to 40% nickel, 28 to 32% chromium, 7 to 9% aluminum, 1 to 2%
silicon, 0.3 to 1% of at least one reactive element of the rare
earths, selectively from 0 to 15% of at least one of the elements
of the group consisting of rhenium, platinum, palladium, zirconium,
manganese, tungsten, titanium, molybdenum, niobium, iron, hafnium,
and tantalum, the total share of the elements of the group being
from 0 to a maximum of 15%, impurities, and a remainder of at least
5% cobalt; and
the component and the coating applied thereon having a ductile
brittle transition temperature below 600.degree. C.
2. The protective coating applied on the component according to
claim 1, wherein the nickel is 25 to 35% by weight, the chromium is
29 to 31% by weight, the aluminum is 7.5 to 8.5% by weight, and the
reactive element of the rare earths is yttrium.
3. The protective coating applied on the component according to
claim 2, wherein the nickel is approximately 30% by weight, the
chromium is approximately 30% by weight, the aluminum is
approximate 8% by weight, the silicon is approximately 1.5% by
weight and the yttrium is approximately 0.6% by weight.
4. A protective coating applied on a component formed of a
nickel-based or cobalt-based superalloy, the protective coating
comprising in percent by weight:
25 to 40% nickel, 28 to 32% chromium, 7 to 9% aluminum, 1 to 2%
silicon, 0.3 to 1% of at least one reactive element of the rare
earths, an addition of from 1 to 15% rhenium, impurities, and a
remainder of at least 5% cobalt.
5. The protective coating applied on the component according to
claim 4, wherein the protective coating and the component have a
ductile brittle transition temperature below 600.degree. C.
6. The protective coating applied on the component according to
claim 1, wherein the protective coating and the component have a
ductile brittle transition temperature below 500.degree. C.
7. The protective coating applied to a component according to claim
4, wherein the addition of rhenium is approximately 7% by
weight.
8. The protective coating applied to a component according to claim
1, wherein the ductile brittle transition temperature is lower than
approximately 450.degree. C.
9. The protective coating applied to a component according to claim
1, wherein the ductile brittle transition temperature is lower than
approximately 400.degree. C.
10. The protective coating applied to a component according to
claim 1, wherein the component is a nickel-based superalloy
consisting essentially of the following elements (in percent by
weight):
0.08 to 0.1% carbon, 12 to 16% chromium, 8 to 10% cobalt, 1.5 to 2%
molybdenum, 2.5 to 4% tungsten, 1.5 to 4.5% tantalum, 0 to 1%
titanium, 0 to 0.1% zirconium, 0 to 1% hafnium, and a balance of
nickel.
11. The protective coating applied to a component according to
claim 1, wherein the component is a nickel-based superalloy
consisting essentially of the following elements (in percent by
weight):
0.08 to 0.1% carbon, 12 to 16% chromium, 8 to 10% cobalt, 1.5 to 2%
molybdenum, 2.5 to 4% tungsten, 1.5 to 4.5% tantalum, 0 to 1%
titanium, 0 to 0.1% zirconium, 0 to 1% hafnium, a minor addition of
boron, and a balance of nickel.
12. The protective coating applied to a component according to
claim 1, wherein said coating has a thickness of between 200 .mu.m
and 300 .mu.m.
13. The protective coating applied to the component according to
claim 10, wherein in the coating the chromium is approximately 30%
and the rare earth is approximately 0.6% yttrium.
14. The protective coating applied to the component according to
claim 10, wherein in the coating the elements of the group
consisting of rhenium, platinum, palladium, zirconium, manganese,
tungsten, titanium, molybdenum, niobium, iron, hafnium, and
tantalum are admixed in a range less than 15%.
15. A protective coating composition resistant to corrosion
consisting essentially of the following elements (in percent by
weight):
approximately 30% nickel, approximately 29 to 31% chromium,
approximately 8% aluminum, approximately 1.5% silicon, 0.3 to 1% of
at least one reactive element of the rare earths, selectively from
0 to 15% of at least one of the elements selected from the group
consisting of rhenium, platinum, palladium, zirconium, manganese,
tungsten, titanium, molybdenum, niobium, iron, hafnium, and
tantalum, impurities, and a remainder of at least 5% cobalt.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a protective coating and to a component on
which the coating is applied, particularly on a gas turbine
component or another component made from a nickel-based or
cobalt-based alloy.
Numerous compositions of protective coatings of alloys which
primarily contain nickel, chromium, cobalt, aluminum and a reactive
element of the rare earths have been developed and tested. One such
coating has become known heretofore from U.S. Pat. No. 4,005,989,
for example. Other coatings of this general type are known from
U.S. Pat. No. 3,928,026 to Hecht et al. and from an article
entitled "The Durability and Performance of Coatings in Gas Turbine
and Diesel Engines" by J. Fairbanks and R. Hecht, Materials Science
and Engineering, 88 (1987), pages 321-330; these papers discuss the
ductility properties of such coatings and their significance in the
gas turbine environment. From U.S. Pat. No. 4,034,142, it is also
known that an additional constituent, silicon, can further improve
the properties of such protective coatings. Although the relatively
wide ranges of the various elements in these documents, in fact, do
suggest qualitatively a way to create protective coatings resistant
to high-temperature corrosion, the compositions disclosed are not
sufficiently specific quantitatively for all purposes.
German Patent 23 55 674 discloses further compositions for
protective coatings, but they are not suitable for uses or
applications of the type which can occur with stationary gas
turbines having a high inlet temperature.
The ductility of protective coatings for gas turbine components is
further discussed in an article by W. Schmidt and G. Lehnert, in
Zeitschrift fur Werkstofftechnik (magazine for materials science),
15 (1984), pages 73-82. The term ductile brittle transition
temperature (DBTT) is introduced in that paper, and thus defined
for the purpose of this text, for a combination of a substrate and
a protective coating. In this context, the protective coating is
deemed to be brittle if it exhibits stress cracking at stresses
below the 0.2% elasticity limit of the substrate. The protective
coating is deemed to be ductile if it exhibits stress cracking only
above the 0.2% elasticity limit of the substrate. The ductile
brittle transition temperature of the combination is defined to be
the threshold temperature below which the protective coating is
brittle and above which it is ductile. In gas turbine applications
it is most desireable to provide protective coatings in which the
ductile brittle transition temperature (DBTT) is fairly low when
combined with suitable substrate materials for the components to
which the coatings are to be applied.
It is accordingly an object of the invention to provide a
protective coating and a component in which the coating has high
resistance to corrosion both at medium temperatures and at high
temperatures, and in which the combination of the component and the
protective coating has a low ductile brittle transition
temperature. The corrosion properties should be improved in the
temperature range from 600.degree. to approximately 1150.degree. C.
so that such protective coatings can be used particularly in
stationary gas turbine systems which operate at partial load or
full load.
With the foregoing and other objects in view, there is provided in
accordance with the invention, a protective coating resistant to
corrosion at medium and high temperatures on a component formed of
nickel-based or cobalt-based alloy, essentially consisting of the
following elements (in percent by weight): 25 to 40% nickel, 28 to
32% chromium, 7 to 9% aluminum, 1 to 2% silicon, 0.3 to 1% of at
least one reactive element of the rare earths, at least 5% cobalt;
and impurities, as well as selectively from 0 to 15% of at least
one of the elements of the group consisting of rhenium, platinum,
palladium, zirconium, manganese, tungsten, titanium, molybdenum,
niobium, iron, hafnium, and tantalum, the combination of the
component and the protective coating having a ductile brittle
transition temperature below 600.degree. C., and preferably below
500.degree. C. Preferably, the chromium content is 29 to 31%.
In this regard, the selective inclusion of a particular element of
the last-mentioned group of elements is based upon knowledge that
the element does not worsen the properties of protective coatings
but, instead, actually improves them, at least under certain
circumstances.
In accordance with an added feature of the invention, the ductile
brittle transition temperature of the combination component/coating
is lower than approximately 450.degree. C. and, advantageously,
lower than approximately 400.degree. C.
In accordance with another feature of the invention, the protective
coating is applied to a component which is a nickel-based
superalloy consisting essentially of the following elements (in
percent by weight): 0.08 to 0.1% carbon, 12 to 16% chromium, 8 to
10% cobalt, 1.5 to 2% molybdenum, 2.5 to 4% tungsten, 1.5 to 4.5%
tantalum, 0 to 1% titanium, 0 to 0.1% zirconium, 0 to 1% hafnium, a
minor addition of boron, and a balance of nickel.
The following properties or significance can be ascribed to the
various constituents of the protective coating:
Cobalt, as a constituent, effects good corrosion properties at high
temperatures.
Nickel improves the ductility of the coating and reduces
interdiffusion with respect to the nickel-based base materials. The
preferred range for nickel is from 25 to 35% and preferably
approximately 30%.
Chromium improves the corrosion properties at medium temperatures
up to approximately 900.degree. C. and promotes the formation of an
aluminum oxide covering film. The preferred range for chromium is
from 28 to 32% and in particular approximately 30%.
Aluminum improves the corrosion properties at high temperatures up
to approximately 1150.degree. C. The share of aluminum should be
about 7 to 9%, the preferred share being from 7.5 to 8.5% and, in
particular, approximately 8%.
Silicon reinforces the action of chromium and aluminum and promotes
the adhesion of the protective oxide film. A favorable range for
the silicon constituent is 1 to 2%, preferably approximately 1.5%.
By means of the addition of silicon, the share of aluminum and/or
of chromium can be reduced from the high content actually desired
for good corrosion properties to the more favorable values for
ductility, without thereby impairing the corrosion properties.
The action of a reactive element, in particular yttrium, is known
per se. The preferred range thereof is from 0.3 to 1% and, in
particular, approximately 0.6%.
In the preferential ranges given, tests have shown particularly
good corrosion properties for the protective coatings for
applications in gas turbines having an inlet temperature above
1200.degree. C.
From prior art literature, various elements have become known which
do not impair the properties of a protective coating, but rather,
in some aspects actually improve them when admixed in a range less
than 15%, and in particular in a share of only a few percent. The
invention of the instant application is also intended to encompass
alloys with such admixtures.
An element which has scarcely been given any consideration for
protective coatings, namely rhenium, can markedly improve the
corrosion properties if it is admixed in a proportion of from 1 to
15%, preferably 4 to 10%, and in particular approximately 7%.
Although rhenium is not as expensive as most noble metals, as a
constituent of a protective coating it can produce properties just
as good as those achieved, for example, by platinum, and can also
be effective even when it constitutes only a small share of the
protective coating.
The coatings according to the invention are applicable by plasma
spraying or vapor deposition (PVD), and they are particularly well
suited for gas turbine blades formed from a nickel-based or
cobalt-based superalloy. Other gas-turbine components, as well,
particularly in gas turbines having a high inlet temperature of
above 1200.degree. C., for example, may be provided with such
protective coatings. The special composition of the coating
according to the invention has proved in tests to be a particularly
suitable selection for stationary gas turbines having a high inlet
temperature. Such tests will be discussed in the following.
EXAMPLES
The components onto which the coatings as previously described are
applied are advantageously manufactured from nickel-based or
cobalt-based superalloys. The components may be formed from:
1. Forging alloys consisting essentially of (in percent by weight):
0.03 to 0.05% carbon, 18 to 19% chromium, 12 to 15% cobalt, 3 to 6%
molybdenum, 1 to 1.5% tungsten, 2 to 2.5% aluminium, 3 to 5%
titanium, optional minor additions of tantalum, niobium, boron
and/or zirconium, balance nickel. Such alloys are known as Udimet
520 and Udimet 720.
2. Casting alloys consisting essentially of (in percent by weight):
0.1 to 0.15% carbon, 18 to 22% chromium, 18 to 9% cobalt, 0 to 2%
tungsten, 0 to 4% molybdenum, 0 to 1.5% tantalum, 0 to 1% niobium,
1 to 3% aluminium, 2 to 4% titanium, 0 to 0.75% hafnium, optional
minor additions of boron and/or zirconium, balance nickel. Alloys
of this type are known as GTD 222, IN 939, IN 6203 and Udimet
500.
3. Casting alloys consisting essentially of (in percent by weight):
0.07 to 0.1% carbon, 12 to 16% chromium, 8 to 10% cobalt, 1.5 to 2%
molybdenum, 2.5 to 4% tungsten, 1.5 to 5% tantalum, 0 to 1%
niobium, 3 to 4% aluminium, 3.5 to 5% titanium, 0 to 0.1%
zirconium, 0 to 1% hafnium, an optional minor addition of boron,
balance nickel. Such alloys are known as PWA 1483 SX, IN 738 LC,
GTD Ill, IN 792 CC and IN 792 DS; IN 738 LC is deemed to be
particularly useful in the context of this invention.
4. Casting alloys consisting essentially of (in percent by weight):
about 0.25% carbon, 24 to 30% chromium, 10 to 11% nickel, 7 to 8%
tungsten, 0 to 4% tantalum, 0 to 0.3% aluminium, 0 to 0.3%
titanium, 0 to 0,6% zirconium, an optional minor addition of boron,
balance cobalt.
It is particularly advantageous to apply coatings having a
thickness between about 200 .mu.m and 300 .mu.m. It has been
observed that in such coatings the DBTT of the combination
coating/component is only marginally dependent on the thickness of
the coating. This provides a substantial amount of operating safety
when applying the coating.
Tests
Several coatings corresponding to prior art coatings and to the
above-described compositions on various components were tested in
burner rig tests performed at the Institute of Materials Science at
the University of Technology Darmstadt, Germany. The tests showed
unexpected results.
The-fuel used in the tests was heating oil EL with 0.5% S, 10 ppm
Na and 8 ppm Cl. The temperature was 850.degree. C. and the tests
lasted for 817 hours. The parameter measured at the end of the
tests was the corrosion depth (in .mu.m).
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a bar graph showing comparative test results of
various coatings.
DETAILED DESCRIPTION OF THE DRAWING
With reference to the graph of the FIGURE, which illustrates the
test results, samples 1 and 2 are prior art coatings as they are
widely used. Sample 2, for instance, largely corresponds to a
coating described in the afore-mentioned U.S. Pat. No. 4,034,142 to
Hecht et al., wherein a part of the silicon has been replaced with
hafnium. Sample 3 is also a prior art coating, a commonly used
protective coating generally of the type described in the
afore-mentioned patent, additionally improved by adding 1.5%
silicon.
With reference to the above-mentioned article by Fairbanks and
Hecht, and particularly FIG. 3 thereof, a coating with nickel,
cobalt, chromium, aluminum, yttrium, silicon and hafnium apparently
led to the best results in a burner rig test. On the basis of the
coating shown in the article, the burner rig tests performed on
order of this inventor included a coating which distinguished
itself from the afore-mentioned patent coatings in the additional
hafnium. The additional hafnium, however, is known from the
pertinent literature, so that the tested sample 2 would appear to
have been one which could have been derived from a combination of
the patent with the state of the art.
With regard to the above classification, samples 1, 3, 4 and 5 had
a base material IN 738 LC and sample 2 had a base material PWA 1438
SX, which is similar to IN 738 LC.
As compared to sample 2, the inventive samples 4 and 5 are clearly
advantageous alone in terms of their corrosion resistance.
As shown in the graph, the prior art samples 1, 2 and 3 exhibited a
corrosion depth of 68 .mu.m, 42 .mu.m and 20 .mu.m, respectively.
The samples produced according to the invention exhibited corrosion
depth of 20 .mu.m and 12 .mu.m, respectively.
Sample 3 has been widely considered the best coating known in the
pertinent art, especially in terms of its corrosion resistance
properties. The coating corresponds to a coating known as GT-29,
developed by General Electric; sample 3 had an additional amount of
silicon, the positive effect of which is now widely acknowledged in
the art. As compared to the inventive coating, sample 3 (GT-29+Si)
has ductility properties which are clearly inferior to the
inventive samples 4 and 5. In other words, sample 3 has a DBTT of
about 600.degree. C., while samples 4 and 5 have a DBTT of about
400.degree. C. and below 600.degree. C., respectively.
It was shown in the rig test that the coatings according to the
invention have an equally good (sample 4) corrosion resistance, or
with added 3% rhenium (sample 5) even an unexpectedly improved
corrosion resistance.
The most unexpected result was the highly improved ductility which
samples 4 and 5 exhibited as compared to sample 3 while not
sacrificing or even improving in terms of corrosion resistance. The
ductile brittle transition temperatures (DBTT) for samples 3-5 are
indicated.
Coatings according to this invention make it no longer necessary to
compromise between corrosion resistance and ductility (important
for tear resistance and adhesion). These properties are not only
optimized relative to each other, but they are vastly improved over
the prior art.
* * * * *